The synthesis of mono-p-nitrobenzyl malonate in toluene by using malonic acid and 4-nitrobenzyl alcohol as raw materials and lipase as catalyst was investigated,and the reaction conditions of enzymatic synthesis were optimized.The optimum conditions were 3 g/L of Novozym 435 and 4 g/L of 4-nitrobenzyl alcohol,4:5 of 4-nitrobenzyl alcohol and malonic acid mole ratio,50 ℃ of reaction temperature,8 h of reaction time.Under above conditions,the yield of mono-p-nitrobenzyl malonate could reach 87.3%.Results demonstrated that the yield of mono-p-nitrobenzyl malonate retained 70% after Novozym 435 being used 6 times.The structure of mono-p-nitrobenzyl malonate was characterized and determined by nuclear magnetic resonance hydrogen spectrum(1H NMR).